Older patients with diabetes who are overly tired during the day may be at a higher risk for hypoglycemia, researchers reported.

Older patients with diabetes who are overly tired during the day may be at a higher risk for hypoglycemia, researchers reported.

In a subgroup analysis from a large observational study, patients who had higher scores on two different scales of daytime sleepiness were significantly more likely to have suffered from severe hypoglycemia (P=0.016 and P=0.024, respectively), Rebecca Reynolds, PhD, of Queen's Medical Research Institute in Edinburgh in Scotland, and colleagues reported online in Diabetes Care.

"In this large cohort of elderly people with type 2 diabetes, those with increased daytime sleepiness, as measured by two different scoring systems, were more likely to have experienced severe hypoglycemia," they wrote.

Sleep-disordered breathing and the daytime tiredness that comes with it are common in type 2 diabetes. To determine whether feeling tired during the day had any link to hypoglycemia severity, the researchers looked at 898 patients with type 2 diabetes from the Edinburgh Type 2 Diabetes Study.

These patients, who had a mean age of 67.9 years, completed two questionnaires on sleep-disordered breathing and daytime sleepiness -- the Epworth Sleepiness Scale and the Berlin Questionnaire -- and they were also asked about severe hypoglycemia.

Overall, the investigators found that patients who scored highly on the Epworth Sleepiness Scale were significantly more likely to have suffered from severe hypoglycemia than those with low scores (15.6% versus 9%, P=0.016).

A positive score in the "sleepiness" category of the Berlin Questionnaire was also associated with a history of previous severe hypoglycemia compared with a negative score (13% versus 8%, P=0.024), they reported.

The overall Berlin score, however, wasn't related to severe hypoglycemia -- and in regression analyses controlling for several factors including age, sex, duration of diabetes, HbA1c, body mass index, and treatment type, the Berlin sleepiness category was no longer significant.

Epworth Sleepiness Scale score, on the other hand, was still a significant predictor of severe hypoglycemia in those analyses.

"Sleepiness as a symptom, rather than sleep-disordered breathing per se, may be a risk factor for hypoglycemia," Reynolds and colleagues wrote. "[Sleepiness] is a non-specific symptom caused by a range of underlying causes and should be differentiated from sleep-disordered breathing and sleep deficiency."

The study was limited by its cross-sectional design, and the findings need to be replicated by collecting prospective data on hypoglycemia and other important confounding factors, the researchers wrote.

But if "further evidence of sleepiness contributing to risk of severe hypoglycemia were available," they concluded, "sleepiness would be another factor to consider in the clinical assessment of hypoglycemia risk."

The study was supported by the Medical Research Council and the Chief Scientist Office of Scotland, the Wellcome Trust, and Pfizer.